import java.util.Scanner;

public class Solution {
    public int longestOnes(int[] nums, int k){
        int ret = 0;
        for(int left=0, right=0, zero=0; right< nums.length;right++){
            if(nums[right] == 0) zero++;//进窗口
            while(zero > k)//判断
                if(nums[left++] == 0) zero--;//出窗口
            ret = Math.max(ret,right-left+1);
        }
        return ret;
    }

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(in.hasNextInt()){
            int size = in.nextInt();
            int[] nums = new int[size];
            for (int i = 0; i < size; i++) {
                nums[i] = in.nextInt();
            }
            int k = in.nextInt();
            Solution solution = new Solution();
            System.out.println(solution.longestOnes(nums, k));
        }
    }
}
